A049601 a(n)=Sum{T(2i,n-2i): i=0,1,...,[ n/2 ]}, array T as in A049600.

0, 0, 2, 3, 12, 25, 76, 182, 504, 1275, 3410, 8811, 23256, 60580, 159094, 415715, 1089648, 2850645, 7466468, 19541994, 51170460, 133951675, 350713222, 918141623, 2403786672, 6293097000, 16475700746, 43133687427, 112925875764

Offset: 0

Author

Clark Kimberling

Keywords

• nonn
• easy

Links

• Index entries for linear recurrences with constant coefficients, signature (2,3,-4,1).

Crossrefs

Cf. A049602.

Formula

G.f.: x^2*(-2+x) / ( (x^2-x-1)*(x^2-3*x+1) ).

a(n) = (Fibonacci(2*n)+(-1)^n*Fibonacci(n))/2. - Vladeta Jovovic, Aug 30 2004